The Amdent Piezo Ultrasonic scalar device, comprises a core device having an oscillation generating part, which can not be sterilised and which is surrounded by an exchangeable, sterilisable, elongated protective housing functioning as a handle. The protective housing is open at its rear end and has an opening having a smaller diameter at its front end. This housing is mountable around the core device sealed with an 0-ring at its rear end towards an unloading socket and at its front end with an O-ring provided around the front of the core device. A scalar tip fixed to or integral with a nipple can be screwed onto the oscillation generating part through an opening at the front end of the sterilised housing first after that the housing has been mounted around the core device. The sterile scalar tip is then surrounded by a particular tip holder during the screwing operation in order to keep the sterilised tip sterile and to protect the operator from being injured by the tip. Thus, in this construction, the housing is not in thorough contact with the vibrating tip or a part of it.